AioPlugin provides support for asynchronous IO event notification. When an external IO event occurs, the event registration causes a Smalltalk semaphore to be signaled. A process can wait on this semaphore, thereby acting as an event handler for the external event. Currently this works with the Unix VM.

UnixAioPlugin implements the primitives that interact with the aio mechanism in the Unix VM. Other platform-specific subclasses could be written to provide a compatible aio mechanism for other platforms.

AioEventHandler provides image side support for aio event notification. An AioEventHandler is an object that waits for an external IO event to occur, then sends #changed to itself. Any object that is interested in the external event can register itself as a dependent of the AioEventHandler, and take appropriate action whenever the external event occurs.